In a wireless communications system, before sending uplink data, a terminal device needs to obtain scheduling information sent by a network device, for example, time-frequency resource allocation and a modulation and coding scheme. In addition, the network device needs to notify the terminal device of power control command information related to uplink transmission. The scheduling information and the power control command information belong to downlink control information (DCI), that is, the DCI is used to schedule data transmission. The DCI used to schedule uplink data transmission may also be referred to as an uplink grant (UL Grant).
In the wireless communications system, a latency (latency) is one of important factors that affect user experience, and continuously emerging new services also impose an increasingly high requirement on the latency. Therefore, in an existing Long Term Evolution (LTE) system, a communication requirement of a low-latency service cannot be met in a transmission mechanism that is based on a transmission time interval (TTI) of one subframe, namely, 1 millisecond. In the existing LTE system, duration of one subframe is 1 millisecond, one subframe is divided into two slots (slot) whose duration is 0.5 millisecond, and each slot includes six or seven symbols. To further reduce a latency, a TTI length of a physical uplink shared channel (PUSCH) needs to be reduced from one subframe to one slot or even shorter. However, in the existing LTE system, all UL grants are used to schedule uplink data whose TTI length is 1 millisecond, and there is a relatively long latency in scheduling uplink data whose TTI length is less than 1 millisecond.